Study On Seismic Performance Of Suspended Ceiling With Mineral Wool Boards

The suspended ceiling(SC)is one type of key nonstructural components in buildings.The SC with mineral wool boards is widely used in public buildings such as office buildings.The earthquake disasters occurring in recent years indicated that the seismic capacity of the SC was insufficient and the SC suffered serious seismic damage,frequently leading to interruption of building function,great economic loss,and even threat to life safety.At present the studies on the seismic performance of the Chinese style SC with mineral wool boards were insufficient.This study focused on the seismic performance of the Chinese style SC with mineral wool boards by experiments and the numerical analysis.The main research work and results are summarized as follows:1.A series of tests on the typical main tee splices,main-cross tee joints and peripheral joints of the SC under monotonic and cyclic loadings were conducted to investigate the mechanical behavior of the joints and splices.The failure modes,load-bearing ability,deformation capacity,force-displacement hysteretic behavior,and energy dissipation capability of different joints and splices were investigated.The test results indicate that the tensile strength and deformation capacity of the main tee splices in the axial test are basically identical to those of the main tee splices subjected to the axial compressive loading.The compressive strength of the main-cross tee joints in the axial test is half of their tensile strength.The tensile strength of the peripheral joints in the axial test is far less than their compressive strength.Compared with the shear capacity of the main-cross tee joints in the strong axis,the joint strength is lower but the deformation ability of the joints is stronger in the weak axis in the shear test.Compared with the bending capacity of the main-cross tee joints in the strong axis,the joint strength is greater but the rotation ability of the joints is slightly lower in the weak axis in the bending test.The energy dissipation capacity of different joints and splices under the given loading modes is limited.2.Based on the cyclic test data of the ceiling gird joints and splices,the Pinching4 model was used to establish the force-displacement hysteretic model for the typical grid joints and splices.The applicability of the Pinching4 model to different gird joints and splices was discussed.The analytical results show that the hysteresis curves and accumulated energy dissipation based on the hysteretic model are consistent with the corresponding experimental results,indicating that the Pinching4 model can accurately reflect the hysteretic behavior of the grid joints and splices.On this basis,the generic force-displacement hysteretic model for various grid joints and splices was further established,and the generic hysteretic model can be used for the nonlinear numerical analysis of the same type of the SC.3.Three kinds of SCs with mineral wool boards and a steel platform used for installing the SCs were designed and constructed.The full-scale shaking table tests on the ceiling specimens were carried out to investigate the seismic damage mechanisms and seismic performance of the SC.The movement characteristics of ceiling grid was studied.The effect of the boundary condition and ceiling types on the acceleration,relative displacement,and strain responses of the SC were compared and discussed.It is found that the seismic performance of the SC is significantly affected by the boundary condition and ceiling types.Among the three boundary condition,the seismic responses of the SC with the fixed-semi-free condition decrease most obviously,and thereof its seismic performance is the best.Although the construction of the single-layer SC is more complicated than that of the double-layer SC,the seismic performance of single-layer SC is better than that of double-layer SC.4.Based on the cyclic test data of the ceiling gird joints and splices,the seismic fragility curves of the ceiling gird joints and splices which reached the failure limit state were established.Based on the shaking table test data of the SCs,the falling seismic fragility curves of the ceiling perimeter components were established,and the seismic pounding analysis on the ceiling perimeter components was carried out.The analytical results show that compared with the single-layer SC,the perimeter components of the double-layer SC is more likely to fall off from the wall angle and collide with the the wall angle.Among the three boundary condition,the perimeter components of the SC with the fixed-semi-free condition has the lowest collision probability with the wall angle.5.Numerical models for the aforementioned SCs with mineral wool boards for shaking table tests were established with the aid of finite element software Open SEES.The effects of the nonlinear behavior of the grid joints and splices,and the friction and impact behavior at the ceiling perimeter on the dynamic responses of the SC were considered in these models.The comparison between the numerical analysis results and test results shows that the models can accurately simulate the acceleration and relative displacement responses of the SC with the free condition and semi-free condition,and are not applicable to the SC with the fixed-semi-free condition.A reinforced concrete frame structure was designed,and elastoplastic time history analysis was carried out by using finite element software Open SEES.The floor waves of the main structure were calculated for the seismic input of numerical model for the SC.The effects of vertical seismic action and floor height on the seismic response of the SC were analyzed.The seismic performance of the SC under the input of three intensities of horizontal earthquakes were studied.The results show that the vertical earthquake has little effect on the seismic performance of the SC,so from the point of view of simplifying the calculation,the effect of vertical seismic action can be ignored when analyzing the seismic response of the SC.At the top floor of the main structure,the maximum axial force of the main-cross joints of the SC is less than its buckling force under the input of three intensity earthquakes,indicating that the seismic performance of the SC is good under earthquakes.The SC at the top floor of the structure will collide with the boundary under the input of three intensity earthquakes,and the degree of collision will increase with the increase of earthquake intensity.The horizontal seismic response of the SC increases with the increase of the floor height under frequent and basic earthquakes;under rare earthquakes,the horizontal seismic response of the SC is greatest at the top floor of the structure,followed by the bottom floor of the structure,and least at the middle floor of the structure.